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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | -3 |
| 4 | 7 |
| 5 | -10 |
| 6 | -18 |
| 7 | 168 |
| 8 | 360 |
| 9 | -19008 |
| 10 | 262080 |
| 11 | -2724480 |
| 12 | 25194240 |
| 13 | -232951680 |
| 14 | 2505444480 |
| 15 | -34676812800 |
| 16 | 577980748800 |
| 17 | -10296734515200 |
| 18 | 185178186547200 |
| 19 | -3347775973785600 |
| 20 | 62005095419904000 |
| 21 | -1204098364514304000 |
[0,0,1,-3,7,-10,-18,168,360,-19008,262080, -2724480,25194240,-232951680,2505444480, -34676812800,577980748800,-10296734515200, 185178186547200,-3347775973785600, 62005095419904000,-1204098364514304000] |